In this double blinded, placebo-controlled trial, we treated stable COPD patients with the NAD precursor nicotinamide riboside (NR) for 6 weeks and followed up 12 weeks after. NAD levels were lower in COPD patients compared with lung-healthy controls and correlated with lung function. NR significantly increased NAD levels, reduced lung inflammation, and cellular senescence in vivo and in vitro. Our findings suggest that NR could be a viable treatment option for COPD patients.